85 



I 



CHAPTER Y. 

 THE ORIGIN OF LIFE. 



ALL our speculations about the first appearance of life on 

 our planet must be based upon the assumption that in times 

 immemorial the earth revolved in the universe as an incandes- 

 cent sphere like those nebulous spots which we still see on the 

 firmament. The process of cooling and condensation brought 

 about the present form of sun, earth, and the other stars. The 

 Law of Evolution, to which every living thing is subject, still 

 rules the world-systems, and if there is one statement in science 

 which we may make with every appearance of truth it is that 

 our earth, which is to the simple mind the prototype of the 

 permanent, was not created spontaneously but has evolved in 

 accordance with this law. 



It is true that experience deserts us here ; it tells us nothing, 

 or only very little, about the history of the world-bodies, but we 

 may, nevertheless, regard the Nebular Theory of Kant-Laplace, at 

 least in its fundamental principles, as one of the surest founda- 

 tions of our conception of Nature. 



Science can never dispense with hypothesis. The most 

 important foundation of our natural philosophy, the Law of 

 Causality, which is so intimately connected with our conscious- 

 ness that without it we are unable to conceive any change, is 

 but a hypothesis which we formulate and force upon Nature so 

 that we may bring order into the chaos of phenomena. To direct 

 observation the causal nexus between two changes is as deeply 

 hidden as, for instance, the origin of the solar system ; what we 

 see and observe is only a variety, a multitude of concurrent or 

 successive phenomena. When we observe that a certain change 

 is regularly followed by another certain change we formulate the 

 hypothesis that the second change is a necessary consequence 



